javascript class property not set in success function of ajax call

Sorry for the duplication but I can find any solution in the others posts.

I'm trying to fill a javascript object using a ajax call to a webservice. I don't understand the logic of this and why my object in not set after the call. I wrote this little example to explain my problem :

Code :

function Cellule(){
    this.test = 0;
    this.textfunction();
}

Cellule.prototype.textfunction = function(){
    this.test = 1;
    $.ajax({
        type: "GET",
        url: "BASEURL/cellules", 
        data: "",
        success: function(msg){
            console.log("success");
            this.test = 2;
            console.log(cellule);
        }
    });
};

var cellule = new Cellule();

Console out :

success
Cellule {test: 1}